Cooler tubes for rotary kiln

ABSTRACT

An improved cooler tube construction for rotary kilns is disclosed which includes a concavo-convex internal surface located at the inlet end of each cooler tube. This concavo-convex surface acts to prevent back-spill and to advance material through the cooler tube.

lted States Patent 11 1 [111 3,11,824 Theil May 21, 1974 [5 COOLER TUBES FOR ROTARY KILN 3.556.495 1/1971 Jensen 432/117 2,904,322 9/1959 Bruff 432/117 [75] Inventor Sven C0Penhage"! 3,279,775 10/1966 Roubal 432/80 Denmark 3,643,933 2/1972 McDonald 432/80 Assigneez F. L & C0. Cresski, 828,555 8/1906 Krottnaurer r. 432/117 {22] Filed: Sept. 13, 1972 Primary Examiner-John J. Camby [21] Appl' Assistant Examiner-Henry C. Yuen Attorney, Agent, or Firm-Pennie & Edmonds Foreign Application Priority Data Sept. 20, 1971 Great Britain 43765/71 [52] US. Cl 432/80, 432/1 16, 34/ 134 ABSTRACT [51] Int. Cl. F27b 7/20 [58] Field of Search 432/103 106, An improved cooler tube construction for rotary kilns 432/80, 83, 1 15, 1 17, 26, 34/134, 135, is disclosed which includes a concave-convex internal 109, 127; /88 surface located at the inlet end of each cooler tube. This concave-convex surface acts to prevent back-spill [5 6] References Cited and to advance material through the cooler tube. UNITED STATES PATENTS V 3,372,915 3/1968 Jensen 432 117 6563 14119154 Drawing Figures PATENTEBmer m4 SHEEI 1 0f 2 r I 1 I /11 COOLER TUBES FOR ROTARY KILN BACKGROUND OF THE INVENTION The invention relates to a rotary kiln of the type having a body or shell and a plurality of cooler tubes arranged in a'planetary fashion around the outlet end of the kiln shell with-each tube connected adjacent one of its ends to an outlet opening in the kiln shell by a communicating chute.

During the rotation of this type of kiln the material to be burnt or sintered falls or slides through the outlet openings and communicating chutes into each cooler tube as it passes through the lowermost point of its path of travel. Air is drawn or blown through the cooler tubes in a direction countercurrent to the hot material so as to cool it and subsequently enters the kiln through the outlet openings through which the hot material passes to the cooler tubes via the chutes. This preheated air is then utilized tosupport combustion within the kiln.

The kiln shell in rotary kilns of the type disclosed herein is generally mounted such that its axis of rotation is inclined upward in the direction opposite to the direction of material movement or flow within the kiln body. In one construction the cooler tubes extend alongside the kiln shell and areinclined upward in the direction in which material flows through the cooler tubes (i.e., in a direction opposite to the direction of material flow through the kilnshell.) Such cooler tubes are commonly known as uphill cooler tubes. In another construction, the cooler tubes extend away from the outlet end of the kiln shell and are inclined downward in the direction in which the material flows through the cooler tubes (i.e., in the same direction as material flow through the kiln 'shell) in which caseth'e cooler tubes v With rotary'kiln constructions of the type described, there is often a tendency for someof the hot material entering each cooler tube when it is in its lower most position below the axis of the kiln to return to the kiln again when the cooler tube reaches its uppermost position above the kiln axis since, when in this latter position, the outlets of thecommunicating chutes are of course above their inlets. This return or back-spill of material is very undesirable because it not only reduces output but also hinders the freepassage of preheated air into the kiln.

Several kiln constructions have been proposed comprising various plate or refractory structures built into the kiln to diminish or prevent back-spill. In one construction the chutes are curved and formed asa part of a helix. In another construction part of theinlet end of the cooler tube is formed as a section of a cylinder the axis of which is inclined to that of the tube so as to provide a surface down which material in the tube may slide during rotation of the tube.

The present invention is specifically concerned with a new and improved construction of the inlet end of a cooler tube to substantially eliminate back spill even when the charge in each cooler tube is larger than normal.

SUMMARY OF THE INVENTION According to the invention the end wall of each cooler tube adjacent the communicating chute includes two or more partial and substantially conical surfaces having a common apex. At least one of the conical surfaces is concave to the interior of the cooler tube. The other conical surface (i.e., the one which is adjacent to the opening into the chute and over which material falling into the tube through the chute first passes upon rotation of the kiln) is convex to the interior of the cooler tube.

The convex surface at the inlet end prevents backspill of material from the cooler tube as this surface conveys the material away from the opening during rotation of the kiln and cooler tubes. The material is then advanced through each cooler tube by the concave surface. The concave surface forms a continuation of the convex surface and acts as a screw conveyor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view, partially in cross section, of a kiln equipped with planetary cooler tubes according to this invention. I

FIG. 2 is a cross-sectional view taken along the lines 2-2 of FIG. 1.

Y FIG. 3 shows the inlet end of a cooler tube according to this invention viewed in an axial direction; and

FIG. 4 is a top plan view of the inlet end of the cooler tube shown in FIG. 3 as viewed in the direction of arrows 4 in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION With reference to FIGS; 1 and 2, rotary kiln l is provided with a'refractory lining 3 for burning of a charge 2 of material (e.g., cement raw material) to clinker.

Near its lower or outlet end the kiln has a plurality of outlet openings 4 communicating through chutes 5 with a corresponding number of cooler tubes 6 mounted with their axes parallel to the axis of the kiln and arranged equiangularly around the end of the kiln in a planetary fashion. As shown each chute 5 includes a first and second part 5a and 5b which are disposed at an angle relative to each other to thereby define a knee-bend 50. In the kiln construction shown in the drawings, the cooler tubes 6 are the up-hill type previously described.

Each cooler tube 6 comprises a cylindrical tube. The end wall of each cooler tube adjacent its inlet end includes a plate 13 forming a concavo-convex surface which, as shown in FIG. 3, comprises partial conical surfaces 7, 8 and 9 having a common apex l2. Surfaces 7, 8 and 9 form a guiding surface for the material as itv begins passage through the cooler tube. The end wall also includes plane closure plates 10 and 11 arranged as shown. Conical surface 7 is convex to the interior of the cooler tube and conical surfaces 8 and 9 are concave to the interior of the cooler tube. The common apex 12 is, in the construction shown, located approximately on or near the axis of the cooler tube. The concavo-convex or curved plate 13 may comprise an infinite number of conical surfaces to achieve the desired curvature although only three such surfaces are depicted in the construction shown in thedrawings.

As shown, the communicating chute leads into the cooler tube in substantially tangential relationship to convex surface 7 and through the interior surface of plane plate 11 which is oriented substantially parallel to the axis of the tube. Convex conical surface 7, in turn, continues into concave conical surfaces 8 and 9. With this arrangement the chute does not interfere with the convex surface 7 or the concave surfaces 8 and 9. In effect, the convex surface serves as a continuation of the communicating chute and facilitates the transfer of material from the chute to the cooler tube. The convex surface at the same time serves as a barrier preventing return of material into the chute which, as previously described, communicates with or opens into the interior of the cooler tube in a plane parallel to the axis of the tube and thereby not directly along the cylindrical surface of the tube.

During rotation of the kiln in the direction indicated by an arrow in FIGS. 2 and 3 part of the charge 2 in the kiln drops into the communicating chute 5 as the opening 4 of the communicating chute passes its lowermost position. The material slides into the cooler tube and reaches at first the lowermost portion of the cylindrical wall of the cooler tube. By further rotation of the cooler tube the material is effectively pushed away from the inlet end by the convex surface 7 and then advanced towards the outlet end of the cooler tube by the concave surfaces 8 and 9. The concave surfaces act as a screw conveyor to push the material forward in the cooler tube.

When each cooler tube passes through its uppermost position the material in the cooler tube may start to slide back towards its inlet end in accordance with the angle of repose of the material. Back-spill normally occurs during movement of the cooler tube through the first 90 after reaching its uppermost position. Substantially all of this back-spill is prevented from reaching the opening into the cooler tube because of the barrier fonned by the convex surface 7. And, due to the position of the inlet opening in the plane plate 11 parallel to the axis of the kiln this back-spilling material cannot reach the opening into the cooler tube even when the cooler tube has a charge filling the cooler tube to fifty percent of its capacity.

In the unlikely event that some small amount of material gets into the communicating chute (due to abovenormal charging of the tube) when it is near the horizontal plane through the axis of the kiln, such material is trapped by the knee bend in the communicating chute and thus prevented from reentering the kiln shell.

The position of the communicating chute renders it possible to thermally insulate the chute separately without insulating or covering part of the inlet end of the cooler tube. This feature is important because this part of the cooler tube is exposed to intense heating by the incoming material and must necessarily radiate part of such heat; otherwise the said heat may cause damage to this part of the cooler tube.

I claim:

1. In a rotary kiln having a plurality of cooler tubes mounted in planetary fashion around the outlet end of the kiln with the inlet end of each tube connected to the outlet end of the kiln by a communicating chute, the improvement wherein at least a portion of the interior end of each cooler tube is defined by at least one concave-convex guiding surface which comprises a first conical surface positioned at the outlet end of the communicating chute and convex to the interior of the cooler tube, a second conical surface positioned adjacent to said first conical surface and concave to the interior of the cooler tube, a third conical surface positioned adjacent to the second conical surface and concave to the interior of the cooler tube, said conical surfaces having a common apex and being positioned and oriented relative to the outlet opening of the communicating chute and the inlet opening of the cooler tube such that when the kiln is rotated, material falling from the outlet end of the rotating kiln into each communicating chute passes over said first conical surface of said guiding surface toward the cooler tube, then over said second and third conical surfaces toward the cooler tube while said first convex conical surface prevents the return of material from the cooler tube into the communicating chute.

2. The improvement according to claim 1, wherein:

a. the inlet end of each cooler tube includes a plane surface oriented substantially parallel to the axis of the cooler tube; and

b. each chute leads into its respective cooler tube substantially tangential to a convex portion of the concavo-convex surface and through said plane surface whereby the chute does not interfere with the concave and convex portions of the concavoconvex surface.

3. The improvement according to claim 2 wherein:

a. the common apex is located substantially on the axis of the tube.

4. The improvement according to claim 3 wherein the interior end of each cooler tube isdefinedby a plurality of concave-convex guiding surfaces such that said interior end of each cooler tube functions as a screw conveyor which transfers material falling from the outlet end of each communicating chute into each cooler tube.

5. The improvement according to claim 4 wherein:

a. each chute includes a first and second pipe section disposed at an angle with respect to each other to thereby define a trap for back-spilling material passing from the respective cooler tube into the kiln shell.

6. The improvement according to claim 5 wherein:

a. said chute is thermally insulated. 

1. In a rotary kiln having a plurality of cooler tubes mounted in planetary fashion around the outlet end of the kiln with the inlet end of each tube connected to the outlet end of the kiln by a communicating chute, the improvement wherein at least a portion of the interior end of each cooler tube is defined by at least one concave-convex guiding surface which comprises a first conical surface positioned at the outlet end of the communicating chute and convex to the interior of the cooler tube, a second conical surface positioned adjacent to said first conical surface and concave to the interior of the cooler tube, a third conical surface positioned adjacent to the second conical surface and concave to the interior of the cooler tube, said conical surfaces having a common apex and being positioned and oriented relative to the outlet opening of the communicating chute and the inlet opening of the cooler tube such that when the kiln is rotated, material falling from the outlet end of the rotating kiln into each communicating chute passes over said first conical surface of said guiding surface toward the cooler tube, then over said second and third conical surfaces toward the cooler tube while said first convex conical surface prevents the return of material from the cooler tube into the communicating chute.
 2. The improvement according to claim 1, wherein: a. the inlet end of each cooler tube includes a plane surface oriented substantially parallel to the axis of the cooler tube; and B. each chute leads into its respective cooler tube substantially tangential to a convex portion of the concavo-convex surface and through said plane surface whereby the chute does not interfere with the concave and convex portions of the concavo-convex surface.
 3. The improvement according to claim 2 wherein: a. the common apex is located substantially on the axis of the tube.
 4. The improvement according to claim 3 wherein the interior end of each cooler tube is defined by a plurality of concave-convex guiding surfaces such that said interior end of each cooler tube functions as a screw conveyor which transfers material falling from the outlet end of each communicating chute into each cooler tube.
 5. The improvement according to claim 4 wherein: a. each chute includes a first and second pipe section disposed at an angle with respect to each other to thereby define a trap for back-spilling material passing from the respective cooler tube into the kiln shell.
 6. The improvement according to claim 5 wherein: a. said chute is thermally insulated. 